Hydrocerussite-related phase NaPb5(CO3)4(OH)3 from the ancient slags of Lavrion, Greece

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Marco E. Ciriotti
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Hydrocerussite-related phase NaPb5(CO3)4(OH)3 from the ancient slags of Lavrion, Greece

Messaggio da Marco E. Ciriotti » mer 09 ago, 2017 5:52

Prossima pubblicazione.

Referenza:
▪ Siidra, O.I., Nekrasova, D.O., Chukanov, N.V., Pekov, I.V., Yapaskurt, V.O., Katerinopoulos, A., Vodouris, P., Magganas, A., Zaitsev, A.N. (2017): Hydrocerussite-related phase NaPb5(CO3)4(OH)3 from the ancient slags of Lavrion, Greece. Mineralogical Magazine, 81, (in press).

Abstract:
The NaPb5(CO3)4(OH)3 phase forms colourless lamellar crystals in cavities within a pebble of the ancient marine slag collected in the Pacha Limani area of the Lavrion mining district, Attiki, Greece. This phase of anthropogenic origin was characterized by the electron microprobe, IR spectroscopy, powder and single-crystal XRD. The unique crystal structure (P63/mmc, a = 5.2533(11), c = 29.425(6) Å, V = 703.3(3) Å3, R1 = 0.047) is based upon structurally and chemically different electroneutral blocks. Each of the blocks can be split into separate sheets. The outer sheets in each block are topologically identical and correspond to the [PbCO3]0 composition. [Pb(OH)2]0 lead hydroxide sheet is sandwiched between the two [PbCO3]0 sheets resulted in the formation of the first block [Pb3(OH)2(CO3)28 2]0 structurally and compositionally identical to that one in hydrocerussite Pb3(OH)2(CO3)2. Similarly [Na(OH)]0 sheet is sandwiched between another two [PbCO3]0 sheets thus forming [NaPb2(OH)(CO3)2]0 block previously described in the structure of abellaite NaPb2(OH)(CO3)2. Stereochemically active lone-electron pairs on Pb2+ cations are located between the blocks. There are two blocks of each type per unit cell, which corresponds to the following formula: [Pb3(OH)2(CO3)2][NaPb2(OH)(CO3)2] or NaPb5(CO3)4(OH)3 in the simplified representation. The formation of NaPb5(CO3)4(OH)3 in Lavrion slags is ensured by the contact of lead-rich slags with the sea water over the last two thousands of years.
Marco E. Ciriotti

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